1. Field of the Invention
The present invention relates to high resolution optical scanners and, more particularly, to a high resolution scanning mechanism for use in a conventional flat bed optical scanner.
2. Description of the Prior Art
Optical scanners are available in a variety of configurations, tailored to the needs of the user. A conventional flat bed scanner includes a light-receiving device mounted in a light-receiving seat, typically a carriage mounted on rails within the scanner housing and is movably adjusted along the rails for scanning line-by-line documents, photographs, transparencies, etc. The light-receiving device includes mirrors and a lens for focusing the image upon an electro-optic transducer, also known as a charge coupled device (CCD) which then converts the light images into electrical signals. These signals are then digitized for use by a computer for reproduction and manipulation of the digitized image by commercially available software. In conventional scanners, the CCD is centrally mounted within the light-receiving device. The device may also include the use of a focusing mechanism for adjusting the distance between the lens and the CCD. While these devices are suitable for low resolution document reproduction, they are unable to provide the necessary resolution required for use with multimedia and digital photographic processing applications.
High resolution optical scanners have been proposed which are generally of a high cost due to the number of CCDs required for high resolution. CCD resolution is determined by the number optical sensors or pixels located linearly across the viewing area. These CCDs can be manufactured to obtain the desired high resolution by increasing the number of pixels per inch. However, high resolution CCDs are not readily available due to the high costs associated with these types of devices. Thus, it would be desirable to provide a high resolution scanner at a low production cost for use by a variety of users.
The primary object of the present invention is to provide a high resolution scanning mechanism for use with a conventional CCD to increase the resolution of the CCD when scanning documents, transparencies and photographs.
Another object of the present invention is to provide a control program for use in a scanner central processing unit to control a motorized high resolution scanning mechanism including a switch mirror to scan documents at high resolutions within a conventional scanner.
The present invention is a mechanism and method for high resolution scanning within a conventional scanner, using a conventional CCD-type image processing device. The mechanism includes a set of mirrors which scan one-half the width of the platen on each pass and focus the one-half width onto the CCD. Upon completion of the first pass, a mirror is switched to direct the image from the other half of the platen onto the CCD. Conventional stitching software is used to align the images without overlap. By this structure and method the resolution of the scanning is increased by a factor of two, but at the expense of having to scan the object twice. Software provided with the scanning device stores each column from the object to be scanned within memory. After the scanner scans in a first column of data, the carriage then returns and scans the remaining column. When the object has been completely scanned, software within the scanner provides the necessary processing for combining the columns of data into one image. With each column scanned at the conventional resolution, the combined image from the columns is at a higher resolution. The resolution achieved from two columns is greater than in normal scanning methods using the same CCD. Thus, a relatively low cost, high resolution scanner is achieved using a conventional CCD. In addition, the mechanism provides a way for upgrading existing scanners to include a high resolution capability by exchanging the existing carriage and software with the present invention.